JP2004198829A - Optical modulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical modulator which can obtain higher elastic force from a movable thin film than a cantilever structured one and which can improve its quick response. <P>SOLUTION: Both ends of the movable thin film 25 are supported with a substrate 21 while separated therefrom via a void 23 and light is reflected on a reflection film 31 formed on the surface of the movable thin film 25. On the other hand, a slope inclined toward the substrate 21 with a specified angle is formed on the movable thin film 25 by displacing only a part of the one end side or a part of the other end side of the movable thin film 25 with electrostatic force with respect to the surface of the substrate 21 so as to make the direction of the light reflected on the reflection film 31 variable by the formation of the slope. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light modulation element in which a movable thin film is displaced or elastically restored (electromechanical operation) by electrostatic force so that the direction of light reflected by the movable thin film can be changed.
[0002]
[Prior art]
There is a light modulation element as a control element that temporally changes the amplitude, phase, and frequency of light. The light modulation element changes the refractive index of a substance that transmits light by an external field applied to the substance, and finally transmits or reflects this substance through optical phenomena such as refraction, diffraction, absorption, and scattering. Control the intensity of light. As one of these, an electromechanical light modulation element that performs light modulation by mechanically operating a movable thin film manufactured by micromachining with electrostatic force is known.
[0003]
Prior art document information related to the invention of this application includes the following.
[Patent Document 1]
JP-A-7-218845 [0004]
As shown in FIG. 10, in the electrostatic mirror device disclosed in Patent Document 1, the reflective layer 3 on which the mirror is disposed is supported by a support member 5, and the support member 5 is a piece. It is supported above the substrate 1 via the cantilever 4. The cantilever 4 is provided on a substrate 1 provided with an insulating film 6. The other end of the support member 5 is connected to the insulating film 6 on the substrate 1 by the adsorption film 2. An electrode 7 is provided between the substrate 1 and the insulating film 6, and the insulating film 6 and the adsorption film 2 are connected above the electrode position. In the figure, 10 indicates incident light and 11 indicates reflected light.
[0005]
In this electrostatic mirror device, when a voltage is applied to the electrode 7, the adsorption film 2 is attracted in the direction of the electrode by electrostatic force, and accordingly, the support member 5 is bent and the reflective layer 3 is inclined. Thereby, the reflection direction of the light incident on the reflective layer 3 can be changed. According to this electrostatic mirror device, it is possible to reduce the size and the integration, and to control the deflection angle of the reflected light over a wider range than the conventional mirror device.
[0006]
[Problems to be solved by the invention]
However, the above-described conventional light modulation element has a so-called cantilever structure in which the reflection layer 3 is supported by the support member 5 and the support member 5 is supported above the substrate 1 via the cantilever 4. A high elastic force from the movable thin film could not be obtained, resulting in a disadvantage in realizing high-speed response. Further, since the adsorption film 2 has to be formed with an inclined surface, there is a possibility that the formation process of the void is complicated and difficult. Furthermore, since the reflective layer 3 is inclined by adsorbing only one adsorption film 2 to the electrode 7, there is a problem that it is difficult to ensure a wide reflection angle range of the reflective layer 3.
The present invention has been made in view of the above circumstances, and a first object of the invention is to provide a light modulation element capable of obtaining a high elastic force from a movable thin film and improving high-speed response compared to a cantilever structure. There is to get. The second object is to obtain a light modulation element capable of simplifying the process of forming the air gap as compared with a cantilever structure in which an inclined surface must be formed. A third object of the present invention is to obtain a light modulation element that can be reflected by a plurality of different inclined surfaces and can widen the reflection angle range.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the light modulation element according to claim 1 of the present invention is characterized in that a movable thin film is supported on a substrate surface at least at both ends with a gap, and light is reflected by a reflective film formed on the surface of the movable thin film. On the other hand, the movable thin film has an inclined surface inclined at a predetermined angle with respect to the substrate surface by reflecting only a part on one end side or a part on the other end side of the movable thin film with respect to the substrate surface by electrostatic force. The direction of the reflected light reflected by the reflective film can be changed by forming the inclined surface.
[0008]
In this light modulation element, the movable thin film is disposed opposite to the substrate surface with a gap, and only a part on one end side or a part on the other end side of the movable thin film is displaced with respect to the substrate surface by electrostatic force. A surface is formed on the movable thin film. By forming the inclined surface, the direction of the reflected light reflected by the reflecting film can be changed. Therefore, compared with the conventional cantilever structure, the number of bending portions of the movable thin film is increased, a high elastic force is obtained from the movable thin film, and high-speed response is improved.
[0009]
The light modulation element according to claim 2 is the light modulation element according to claim 1, wherein the movable thin film is made of a single material, and the movable part is connected to both ends of the movable part so as to be movable. And a support part for supporting the part on the substrate surface with the gap therebetween.
[0010]
In this light modulation element, the movable thin film is made of a single material, and the movable part of the movable thin film is arranged in parallel to the substrate surface with a gap. Therefore, the void formation process is simplified compared to a cantilever structure in which an inclined surface must be formed.
[0011]
A light modulation element according to a third aspect is the light modulation element according to the first aspect, wherein the movable thin film is supported on the substrate surface by a separate column member.
[0012]
In this light modulation element, since the movable thin film is supported on the substrate surface by a separate column member, the gap can be easily formed wide by changing the formation height of the column member. As a result, a deformation operation with a large difference in height is possible in the movable thin film, and a wide reflection angle range can be secured.
[0013]
A light modulation element according to a fourth aspect is the light modulation element according to the third aspect, wherein the column member is made of a material having a lower spring constant than the movable thin film.
[0014]
In this light modulation element, the column member is made of a soft material having a lower spring constant than the movable thin film, so that the bending resistance of the movable thin film is reduced, the high-speed response is improved, and the drive voltage can be lowered. Become.
[0015]
The light modulation element according to claim 5 is the light modulation element according to claim 1, 2, or 3, wherein a plurality of electrodes for generating an electrostatic force on the movable thin film are provided on at least one of the substrate surface and the movable thin film. A part of the movable thin film is formed and can be displaced for each of the electrodes.
[0016]
In this light modulation element, a part of the movable thin film can be displaced for each electrode, and reflection can be performed by a plurality of different inclined surfaces. Therefore, a wide reflection angle range can be secured by combining these different reflecting surfaces.
[0017]
A light modulation element according to a sixth aspect is the light modulation element according to the first, second, or third aspect, wherein the reflective film is a multilayer reflective film.
[0018]
In this light modulation element, since the reflection film is formed of a multilayer reflection film, the reflectance is higher than that of the metal reflection film alone, light absorption of the reflection film is reduced, and heat generation due to light absorption of the reflection film is reduced. . Thereby, the high power tolerance with respect to the high output light source in a reflection type light modulation element is improved.
As used herein, the term “multilayer reflective film” includes a dielectric multilayer reflective film and a dielectric multilayer reflective film provided with a metal half mirror.
[0019]
The light modulation element according to claim 7 is the light modulation element according to claim 1, 2, or 3, wherein the incident light or the emitted light / incident light and the emitted light are condensed on the light incident / exit side. An array is provided.
[0020]
In this light modulation element, incident light or emitted light / incident light and emitted light are collected by a microlens array, so that the light utilization efficiency is increased, and high-efficiency and bright modulated light can be obtained even in a small aperture area. Become. In addition, the light utilization efficiency is increased, and the reflective film can be made smaller than when no microlens is provided, the amount of displacement of the reflective film can be reduced, and the driving energy of the reflective film (that is, the movable thin film) can be reduced. It becomes.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a light modulation element according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view of an embodiment in which the movable thin film of the light modulation element according to the present invention is made of a single material, and FIG. 2 is an operation explanatory view of the light modulation element shown in FIG.
[0022]
As shown in FIG. 1, the light modulation element 100 according to this embodiment includes a substrate 21 and a movable thin film 25 whose central portion is opposed to the upper surface of the substrate 21 in parallel with a gap 23 therebetween. Have as. The movable thin film 25 has elasticity, and is formed in a bridge shape in which both end portions are bonded onto the substrate 21 and the central portion is levitated. The movable thin film 25 is made of a single material, and includes a movable portion 27 and a support portion 29 that is connected to both ends of the movable portion 27 and supports the movable portion 27 on the substrate 21 with a gap 23 therebetween. A fixed electrode 37 is provided on the substrate 21 facing the movable portion 27. As the movable thin film 25, for example, a semiconductor such as polysilicon, an insulating silicon oxide, or a silicon nitride can be used in addition to a ceramic or a resin.
[0023]
A reflective film 31 is formed on the surface of the movable thin film 25, and the reflective film 31 reflects incident light. In the movable thin film 25, for example, only a part of one end side (the right end side in FIG. 1) where the fixed electrode 37 is disposed is displaced (changed in position so as to be close) with respect to the substrate 21 by electrostatic force. As shown, an inclined surface 33 that is inclined at a predetermined angle with respect to the substrate 21 is formed. As a result, the reflective film 31 deposited integrally with the movable thin film 25 also forms the same inclined surface 33. The light modulation element 100 can change the direction of the reflected light reflected by the reflective film 31 by forming the inclined surface 33.
[0024]
When using a high output light source, the reflective film 31 is preferably a dielectric multilayer reflective film. Since the reflection film 31 is made of a dielectric multilayer reflection film, the reflectance is increased as compared with the metal reflection film alone, the light absorption of the reflection film 31 is reduced, and the heat generation due to the light absorption of the reflection film 31 is reduced. Thereby, the high power tolerance with respect to the high output light source in the reflection type light modulation element 100 is enhanced.
[0025]
The light modulation element 100 is formed in an array with a plurality of movable thin films 25 arranged, for example, in a one-dimensional or two-dimensional manner. The movable thin film 25 is elastically deformed by the adsorption force toward the substrate 21 due to electrostatic force, and is displaced so that a part thereof is in close contact with the upper surface of the substrate 21 as shown in FIG. As shown in FIG. 1, a part thereof again floats and is arranged at a position separated by the gap 23 by the elastic return force.
[0026]
The flying height of the movable thin film 25 is determined by the gap 23. The height of the gap 23 is, for example, about 0.1 μm to 10 μm. This void 23 can be usually formed by etching and removing a sacrificial layer (a layer to be removed later to form a void).
[0027]
The substrate 21 has a structure in which a glass substrate 35, a fixed electrode 37, an insulating film (not shown), and the like are sequentially stacked. The movable thin film 25 includes a reflective film 31 and a movable electrode (not shown). In the light modulation element 100, static electricity is generated between the fixed electrode 37 and the movable thin film 25 by applying a voltage to the fixed electrode 37 and the movable electrode, and the movable thin film 25, that is, the Coulomb force due to the static electricity is generated. The reflective film 31 is displaced (electromechanical operation). In addition to the glass substrate 35, a silicon substrate, a support (a film such as PET or polyimide), or the like can be applied to the substrate 21.
[0028]
As the fixed electrode 37 and the movable electrode, for example, metal thin films such as gold, silver, palladium, zinc, aluminum and nickel can be used, metal oxides such as ITO and IZO, very thin metal thin films, and metal fine particles. A thin film dispersed in a transparent insulator or a wide-hand gap semiconductor highly doped can be used.
[0029]
According to this light modulation element 100, the movable thin film 25 is disposed opposite to the substrate 21 with a gap 23 therebetween, and only a part on one end side or a part on the other end side of the movable thin film 25 is against the substrate 21 by electrostatic force. By displacing, the inclined surface 33 is formed on the movable thin film 25. By forming the inclined surface 33, the direction of the reflected light reflected by the reflective film 31 can be changed. Therefore, compared with the conventional cantilever structure, the number of bending portions of the movable thin film 25 is increased (increased to two locations shown in FIG. 2), and a high elastic force from the movable thin film 25 is obtained, so that high-speed response is enhanced.
[0030]
The movable thin film 25 is made of a single material, and the movable portion 27 of the movable thin film 25 is arranged in parallel with the substrate 21 with the gap 23 therebetween. Therefore, the formation process of the space | gap 23 becomes easy compared with the cantilever structure in which the inclined surface 33 must be formed.
[0031]
Next, a second embodiment of the light modulation element according to the present invention will be described.
FIG. 3 is a cross-sectional view of an embodiment in which a plurality of electrodes of the light modulation element according to the present invention are provided, and FIG. 4 is an operation explanatory view of the light modulation element shown in FIG. In the following embodiments, the same members as those shown in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.
[0032]
In the light modulation element 200 according to this embodiment, a plurality of (two in this embodiment) fixed electrodes 37 a and 37 b that generate an electrostatic force on the movable thin film 25 are provided on the substrate 21. The movable thin film 25 is configured such that a part of the movable thin film 25 is displaced for each of the fixed electrodes 37a and 37b. That is, when a voltage is applied to the fixed electrode 37a and the movable electrode, as shown in FIG. 4A, a part of the left side of the movable thin film 25 is displaced, and a voltage is applied to the fixed electrode 37b and the movable electrode. Then, as shown in FIG. 4B, a part of the right side of the movable thin film 25 is displaced. As a result, two inclined surfaces 33 a and 33 b that are symmetrical with respect to a virtual line perpendicular to the substrate 21 are formed at the center of the movable thin film 25.
Instead of the plurality of fixed electrodes 37a and 37b, a plurality of movable electrodes (not shown) are formed, or both of the fixed electrodes 37a and 37b and the movable electrodes are formed and a voltage is applied between the corresponding electrodes. Then, a part of the movable thin film 25 may be displaced. However, even when a plurality of movable electrodes are formed, it is a matter of course that the reflective film 31 is continuously provided between these movable electrodes.
[0033]
According to the light modulation element 200, a part of the movable thin film 25 can be displaced for each of the fixed electrodes 37a and 37b, and reflection can be performed by a plurality of different inclined surfaces 33a and 33b. Therefore, a wide reflection angle range can be secured by the combination of these different inclined surfaces 33a and 33b.
[0034]
Next, a third embodiment of the light modulation element according to the present invention will be described.
FIG. 5 is a cross-sectional view of an embodiment in which the movable thin film of the light modulation element according to the present invention is supported on the substrate surface by a separate column member, and FIG. 6 is an operation explanatory view of the light modulation element shown in FIG.
[0035]
In the light modulation element 300 according to this embodiment, the movable thin film 25 includes only a flat movable portion 27, and the movable portion 27 is supported via a column member 41. The upper end of the column member 41 is joined to the movable portion 27. That is, the movable thin film 25 in the present embodiment is supported on the substrate 21 by the separate column member 41.
[0036]
Here, the column member 41 is made of a material having a lower spring constant than the movable thin film 25. Thereby, the pillar member 41 serves as a cushion layer. This cushion layer facilitates the movement of the movable portion 27 by an external force. In addition, this material needs to be capable of film formation and patterning. Examples of such materials include polyimide, photoresist, polycarbonate, polyethylene, polystyrene, other resins, and organic substances.
[0037]
In this light modulation element 300, for example, only a part of one end side (the right end side in FIG. 6) is displaced (position is changed so as to be close) with respect to the substrate 21 by electrostatic force, so that a predetermined angle with respect to the substrate 21. An inclined surface 33 inclined at is formed. As a result, the reflective film 31 deposited integrally with the movable thin film 25 also forms the same inclined surface 33. The light modulation element 300 can change the direction of the reflected light reflected by the reflective film 31 by forming the inclined surface 33.
[0038]
According to this light modulation element 300, the movable thin film 25 is supported on the substrate 21 by the separate column member 41. Therefore, the gap 23 can be easily formed wide by changing the formation height of the column member 41. It becomes possible. As a result, the movable thin film 25 can be deformed with a large height difference, and a wide reflection angle range can be secured. In addition, since the column member 41 is made of a material having a lower spring constant than the movable thin film 25, the bending resistance of the movable thin film 25 is reduced, the high-speed response is improved, and the drive voltage can be lowered.
[0039]
Next, a fourth embodiment of the light modulation element according to the present invention will be described.
7 is a sectional view of an embodiment in which the movable thin film of the light modulation element according to the present invention is supported on the substrate surface by a separate column member and a plurality of electrodes are provided, and FIG. 8 is a light modulation element shown in FIG. FIG.
The light modulation element 400 according to this embodiment is a support structure using the column member 41 described in the third embodiment, and includes a plurality of fixed electrodes 37a and 37b described in the second embodiment. It has a configuration.
[0040]
Therefore, when a voltage is applied to the fixed electrode 37a and the movable electrode, as shown in FIG. 8A, a part of the left side of the movable thin film 25 is displaced, and a voltage is applied to the fixed electrode 37b and the movable electrode. Then, as shown in FIG. 8B, a part of the right side of the movable thin film 25 is displaced. As a result, two inclined surfaces 33 a and 33 b that are symmetrical with respect to a virtual line perpendicular to the substrate 21 are formed at the center of the movable thin film 25.
[0041]
According to the light modulation element 400, the combination of the inclined surfaces 33a and 33b different from the light modulation element 200 according to the second embodiment makes it possible to secure a wide reflection angle range, and the third embodiment. Similar to the light modulation element 300 according to the configuration, the movable thin film 25 can be deformed with a large difference in elevation, and a wide reflection angle range can be secured. Moreover, the bending resistance of the movable thin film 25 is reduced, and high-speed response is achieved. In addition to being increased, the drive voltage can be lowered.
[0042]
Next, a fifth embodiment of the light modulation device according to the present invention will be described.
FIG. 9 is a cross-sectional view of an embodiment provided with a microlens array of a light modulation element according to the present invention.
The light modulation element 500 according to this embodiment is provided with a microlens array 51 that condenses incident light or emitted light / incident light and emitted light on the light incident / exit side of the substrate 21. The microlens array 51 has a plurality of microlenses 53 located in the incident optical path and the reflected optical path. The microlens array 51 is fixed integrally with the substrate 21 at a predetermined distance by a spacer or the like (not shown).
[0043]
According to this light modulation element 500, incident light or outgoing light / incident light and outgoing light are collected by the microlens array 51, the light utilization efficiency is increased, and high-efficiency and bright modulated light is obtained even in a small aperture area. It will be obtained. Further, the light use efficiency is increased, and the reflective film 31 can be formed smaller than the case where the microlens 51 is not provided, the amount of displacement of the reflective film 31 can be reduced, and the reflective film (that is, the movable thin film 25) 31 is driven. Energy can be reduced.
[0044]
【The invention's effect】
As described above in detail, according to the light modulation element of the first aspect of the present invention, only a part on one end side or a part on the other end side of the movable thin film is displaced with respect to the substrate surface by electrostatic force. In this way, an inclined surface inclined at a predetermined angle with respect to the substrate surface is formed on the movable thin film, and the direction of the reflected light reflected by the reflective film can be changed by forming this inclined surface. High elastic force can be obtained from the thin film, and high-speed response can be improved.
[0045]
According to the light modulation element of claim 2, the movable thin film is made of a single material, and the movable part is connected to both ends of the movable part so as to support the movable part on the substrate surface with a gap. Therefore, the void formation process can be simplified as compared with a cantilever structure in which an inclined surface must be formed.
[0046]
According to the light modulation element of the third aspect, since the movable thin film is supported on the substrate surface by a separate column member, a wide gap can be formed and a wide reflection angle range can be secured.
[0047]
According to the light modulation element of claim 4, since the column member is made of a material softer than the movable thin film, the bending resistance is reduced, the high-speed response is improved, and the drive voltage can be lowered. Can do.
[0048]
According to the light modulation element of claim 5, a plurality of electrodes that generate electrostatic force on the movable thin film are provided on the substrate surface, and a part of the movable thin film can be displaced for each electrode. Reflection is possible by the surface, and the reflection angle range can be widened.
[0049]
According to the light modulation element of the sixth aspect, since the reflection film is a dielectric multilayer reflection film, the light absorption of the reflection film is reduced, and the heat generation due to the light absorption of the reflection film is reduced. As a result, it is possible to enhance the high power resistance against the high output light source in the reflection type light modulation element.
[0050]
According to the light modulation element of the seventh aspect, since the incident light or the emitted light / the incident light and the microlens array for collecting the emitted light are provided on the light incident / exit side, the light use efficiency is increased. Even with a small opening area, high-efficiency and bright modulated light can be obtained. In addition, since the light use efficiency is increased and the microlens is not provided, the reflective film can be made smaller, so that the amount of displacement of the reflective film can be reduced and the driving energy of the reflective film (ie, the movable thin film) can be reduced. Is possible.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an embodiment in which a movable thin film of a light modulation element according to the present invention is made of a single material.
FIG. 2 is an operation explanatory diagram of the light modulation element shown in FIG. 1;
FIG. 3 is a cross-sectional view of an embodiment in which a plurality of electrodes of a light modulation element according to the present invention are provided.
4 is an operation explanatory diagram of the light modulation element shown in FIG. 3. FIG.
FIG. 5 is a cross-sectional view of an embodiment in which a movable thin film of a light modulation element according to the present invention is supported on a substrate surface by a separate column member.
6 is an operation explanatory diagram of the light modulation element shown in FIG. 5. FIG.
FIG. 7 is a cross-sectional view of an embodiment in which a movable thin film of a light modulation element according to the present invention is supported on a substrate surface by a separate column member and a plurality of electrodes are provided.
8 is an operation explanatory diagram of the light modulation element shown in FIG. 7. FIG.
FIG. 9 is a cross-sectional view of an embodiment provided with a microlens array of a light modulation element according to the present invention.
FIG. 10 is a cross-sectional view of a conventional light modulation element having a cantilever structure.
[Explanation of symbols]
21 Substrate surface 23 Gap 25 Movable thin film 27 Movable portion 29 Support portion 31 Reflective film 33 Inclined surfaces 37a, 37b Multiple electrodes 41 Column member 51 Microlens array 100, 200, 300, 400, 500 Light modulation element

Claims (7)

On the substrate surface, the movable thin film is supported at least at both ends with a gap, and the light is reflected by the reflective film formed on the surface of the movable thin film,
The movable thin film is formed with an inclined surface inclined at a predetermined angle with respect to the substrate surface by displacing only a part on one end side or the other end side of the movable thin film with respect to the substrate surface by electrostatic force,
An optical modulation element characterized in that the direction of reflected light reflected by the reflective film can be varied by forming the inclined surface. The light modulation element according to claim 1,
The movable thin film is
Made of a single material,
An optical modulation element comprising: a movable part; and a support part that is connected to both ends of the movable part and supports the movable part on the substrate surface with the gap therebetween. The light modulation element according to claim 1,
The movable thin film is
The light modulation element is supported on the substrate surface by a separate column member. The light modulation element according to claim 3,
The column member is
An optical modulation element comprising a material having a lower spring constant than the movable thin film. The light modulation element according to claim 1, 2, or 3,
A plurality of electrodes for generating an electrostatic force on the movable thin film are formed on at least one of the substrate surface and the movable thin film, and a part of the movable thin film can be displaced for each of the electrodes. element. The light modulation element according to claim 1, 2, or 3,
The light modulation element, wherein the reflection film is a multilayer reflection film. The light modulation element according to claim 1, 2, or 3,
A light modulation element comprising a microlens array for collecting incident light or emitted light / incident light and emitted light on a light incident / exit side.

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